The invention relates to process gas conditioning for tobacco dryers. In particular, the invention relates to a device for conditioning process gas for a tobacco dryer, a vaporization unit for introducing water vapor into the flow of process gas in a tobacco dryer, and to a method for conditioning process gas for a tobacco dryer, in particular a flow dryer.
In the tobacco industry, various methods of drying tobacco are known, for example passing the tobacco through a drum, as is described in DE 22 40 682 C2, or passing the tobacco through a tunnel conveyor, as is described in for example DE 29 04 308 C2. In all cases, it is very important for the tobacco to exhibit a particular moistness at the output of the dryer, which may vary only over a very small range. In order to be able to maintain tobacco moistness at all times, DE 22 40 682 C2 for example propose adding hot water or vapor directly into the moisture drum, while in accordance with DE 29 04 308 C2, water is directly added in the tunnel conveyer. When the water is added directly, there is always the disadvantage that optimum vaporization cannot be achieved, such that clumps are formed. If vapor is introduced separately and directly into a drum, for example into a moisture drum as described in DE 22 40 682 C2, then on the one hand there is an increased expenditure in apparatus, and on the other hand there is no guarantee that the vapor optimally mixes with the actual hot process gas, which could lead to a non-homogenous degree of moisture within the tobacco bulk.